Utils: Preserve output order with merged channels

Restored the process channel mode members to ProcessSetupData and
StartProcessPacket and forward to the QProcess created in
LaunchSocketHandler. LaunchSocketHandler now avoids reading from stderr
for merged channels since it's guaranteed to not be available.

This avoids asserts in Qt 6.3.0 and warnings in Qt 6.3.1 while
preserving the original output order when an application has a mix of
stdout and stderr output.

Change-Id: I9f4541932cf9d8638b38658a5efea9cb5f1798f3
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>

src/libs/utils/launcherpackets.cpp

@@ -64,6 +64,7 @@ void StartProcessPacket::doSerialize(QDataStream &stream) const
            << env
            << int(processMode)
            << writeData
+           << int(processChannelMode)
            << standardInputFile
            << belowNormalPriority
            << nativeArguments
@@ -75,12 +76,14 @@ void StartProcessPacket::doSerialize(QDataStream &stream) const
 void StartProcessPacket::doDeserialize(QDataStream &stream)
 {
     int processModeInt;
+    int processChannelModeInt;
     stream >> command
            >> arguments
            >> workingDir
            >> env
            >> processModeInt
            >> writeData
+           >> processChannelModeInt
            >> standardInputFile
            >> belowNormalPriority
            >> nativeArguments
@@ -88,6 +91,7 @@ void StartProcessPacket::doDeserialize(QDataStream &stream)
            >> unixTerminalDisabled
            >> useCtrlCStub;
     processMode = Utils::ProcessMode(processModeInt);
+    processChannelMode = QProcess::ProcessChannelMode(processChannelModeInt);
 }